The present invention relates to an apparatus and method for determining whether all of the contents of an envelope have been removed, and more particularly to such an apparatus and method which is particularly well-suited for use with envelopes having inconsistent style, color and size.
One of the most crucial considerations for fast and efficient extraction of an envelope""s contents from a large quantity of envelopes is verifying that envelopes passing through the system are in fact emptied of all their contents. Whether the contents of the envelope are extracted directly by an operator""s hand or by other means (typically automated means), there is a possibility that some of the contents of the envelope, such as a check or an important document, will remain stuck to one side of the envelope even when the opposing faces of the envelope are spread apart. In some envelopes, the contents may have been inserted folded, and others not. In some envelopes, the contents may be bunched to one side, rather than neatly centered within the envelope. Obviously, the accidental discarding of checks must be avoided. Even the loss of documents, such as copies of invoices which accompany the checks, is clearly undesirable. For a recipient of a large quantity of checks, such as a utility or a credit card company, the resulting confusion and delay in document processing can be expensive.
In an attempt to remedy these problems, many systems have been developed which are designed to ensure that all of an envelope""s contents have been removed. Examples of such systems include those disclosed in U.S. Pat. Nos. 3,979,884, 4,934,892 and U.S. Reissue Patent No. Re. 32,328. Each of these prior art systems operates by measuring the transmissivity of radiant energy, such as visible light, infrared light, or sound, through the envelope and any contents therein. In general principle, an empty envelope will allow a certain quantity of light to pass through to a photocell, while an envelope having documents remaining therein will allow a lesser quantity of light to pass through to the photocell. This lesser light transmissivity of an envelope still containing a document or documents is used to signal, through a control system, that the envelope then passing by the photocell still contains documents.
More specifically, each of the above described systems generally operates by using a fixed threshold value of light transmissivity, which threshold value is used to indicate the presence or absence of an empty envelope. When the intensity of the light passing through an envelope is above the threshold value, the envelope is deemed empty, and when this intensity is below the threshold value, the envelope is deemed to be not empty. As a result, the effectiveness of the apparatus is highly dependent on the exact value of the threshold in relation to the characteristics of the envelope being subjected to extraction. To allow for variation of the threshold value, prior art devices typically include an external knob which operates as a potentiometer.
Another prior art system designed to ensure that all of an envelope""s contents have been removed is disclosed in U.S. Pat. No. 5,134,834. This prior art reference attempts to remedy a perceived disadvantage of prior art devices in that, no matter how carefully a threshold value is selected for identifying an empty envelope, there will nevertheless tend to be some error because a spread-open envelope which is actually empty may be observed to transmit less light than an envelope still having contents therein. The reference, therefore, attempts to more precisely define an appropriate threshold value by measuring the transmissivity of the envelope and contents when the envelope is unspread and then again after the envelope is spread, and calculating, based on the measured transmissivities of the envelope when spread and unspread, a threshold value of transmissivity consistent with the envelope being empty. After the empty envelope constant is obtained, the series of envelopes are processed. For each envelope in the series, the transmissivity is observed in two states: when the envelope is unspread, and then when the envelope is spread, but with the contents remaining therein. These observed transmissivities are then combined with the empty envelope constant to calculate a target value of transmissivity which would be consistent with a fully emptied envelope. This target value is then used as the threshold transmissivity value for determining when the particular envelope being opened has been emptied of all contents.
All of the prior art devices set forth above, however, suffer from disadvantages of their own. One of such disadvantages relates to the handling of xe2x80x9cwhitexe2x80x9d mail. Mixed mail, also known as xe2x80x9cwhitexe2x80x9d mail consists of envelopes that are inconsistent in style, color, and size. The contents in these envelopes are also inconsistent, containing various types of remittance and correspondence which vary in the number of pages, some of which are folded, the way in which pages are attached together, etc.
Known prior art devices are designed to handle bulk or remittance type mail, which are returned using identical standard envelopes, and cannot be used effectively to process white mail. This is true because all of the known prior art devices use a constant threshold value in order to determine whether or not an envelope is empty. This is true even of U.S. Pat. No. 5,134,834. Although this reference employs a somewhat more sophisticated analysis than the other prior art references described above, the system disclosed therein still employs an empty envelope constant which, once determined, is used in determining whether a series of envelopes is fully emptied.
Using such systems to determine whether white mail envelopes are empty provides inconsistent results at best. These systems cannot take into account all of the potential variations in envelope selection by the sender in a white mail situation. As such, comparing these envelopes having widely varying characteristics to predetermined threshold values or envelope constants is ineffective. For example, a very thin and light transmissive envelope containing a check may have light transmissivity identical to, or even greater than, a thick, light restrictive envelope which has been emptied. Prior art systems provide no mechanism for distinguishing the two cases from one another. As such, no reliable threshold could be set to assure that the emptied light restrictive envelope could be distinguished from the full light transmissive envelope.
What is desired, therefore, is an empty envelope assurance system which determines whether all of the contents of an envelope have been removed, which can be used to effectively and efficiently process white mail having envelopes that are inconsistent in style, color, and size, and which is dependent upon the characteristics of the envelope itself rather than predetermined threshold values or constants.
Accordingly, it is an object of the present invention to provide an empty envelope assurance system which determines whether all of the contents of an envelope have been removed.
Another object of the present invention is to provide an empty envelope assurance system having the above characteristics and which can be used to effectively and efficiently process white mail having envelopes that are inconsistent in style, color, and size.
A further object of the present invention is to provide an empty envelope assurance system having the above characteristics and which is dependent upon the characteristics of the envelope itself rather than predetermined threshold values or constants.
These and other objects of the present invention are achieved by provision of an empty envelope assurance system which includes a conveyor for conveying an opened envelope having a front face and a rear face along a path of movement. The front face and the rear face of the envelope each define a plurality of zones, and the conveyor is arranged such that any contents of the envelope rests against either the front face or the rear face. A first sensor measures a thickness of the front face and any contents resting thereagainst at a plurality of locations in each zone, and generates a signal having a value indicative of the thickness at each location. A second sensor measures a thickness of the rear face and any contents resting thereagainst at a plurality of locations in each zone, and generates a signal having a value indicative of the thickness at each location.
A signal processor receives the signals generated by the first sensor and the second sensor, averages the values of the signals generated by the first sensor at each location to determine an average value indicative of the thickness at each zone of the front face and averages the values of the signals generated by the second sensor at each location to determine an average value indicative of the thickness at each zone of the rear face. Next, the signal processor averages the values of the zones of the front face to determine a value indicative of the thickness of the front face and averages the values of the zones of the rear face to determine a value indicative of the thickness of the rear face. Finally, the signal processor compares the value indicative of the thickness of the front face with the value indicative of the thickness of the rear face to determine whether they correspond within a predetermined limit to determine whether the envelope contains any contents.
The invention and its particular features and advantages will become more apparent from the following detailed description considered with reference to the accompanying drawings.